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SYNCHRO -SETTE 



THE SUBSCRIPTION MAGAZINE RM HU MICROCOMPUTER 

TIMEX - SINCLAIR 




THIS MCNTH’S PROGRAMS 2 

EDITOR RAMBLINGS 6 

THE COMPUTER TUTOR - simulating DRAW & CIRCLE 9 

LETTERS TO THE EDITOR 11 . 

TS-2068 SCREEN MEMORY MAP 13 

DRAWING ELLIPSOIDS ON THE TS-2068 15 



VOLUME 3 ~ NUMBER 3 - MARCH 1984 - CASSETTE' ISSUE - $10.00 



SYCHRO - SETTE IS PUBLISHED MONTHLY BY : THE S & S COMPANY 
HI W. LAKE ST. APPISOH ILL A01P1 (3121 «»-«»» 



fhis Month's Programs 




Ti,ere are 7 programs on 
this month's cassette, not 
counting the LOADER program. 

The program names are as 
they appear on the above menu, 
which is similar to what will 
appear on the screen when the 
LOADER program is running. 

Each program is recorded 
only once on each side of the 
cassette. The first programs 
that can be LOADed will be of 
the small size followed by the 
larger sized programs. The 
other side of the cassette is 
a duplicate of the first 
side. 

Feu: you new subscribers who 
aren't familiar with IOADing 
procedures for cassette 
programs , follow these 
directions : 

A - Make sure that the volume 
setting of the recorder is set 
at about 80 % maximum. 



B - If you have a Bass and/or 
Treble control on the 
recorder, make sure the Treble 
is at maximum and the Bass is 
at minimun. 

C - To LOAD the first program, 
type in LOAD "" and press the 
ENTER key on the computer. 
Then press the PLAY button of 
the recorder. The lead time on 
the NOV/83 cassette is about 
10 seconds until the first 
program begins. 

The time needed to load the 
LOADER program is 48 seconds. 
When the program is loaded, a 
list of this month's programs 
will appear automatically. 

Shut off the recorder when 
the LOADER program is loaded. 
Any of the listed programs can 
new be loaded into the 
computer by pressing the 
appropriate number on the 
keyboard and then pressing the 
PLAY key on the recorder. The 




ly&L v . tflO 

loader program loads by 
searching for the name of the 
program you want and ignoring 
any of the other programs it 
may encounter along the way. 

If you want to go directly 
to a program without waiting, 
we suggest you first find the 
tape location of the beginning 
of each of the programs with 
your recorder counter . This 
can be done as you go through 
the programs the first time, 
noting the tape location on 
the counter as each one is 
being loaded. 

If you don't have a 
counter, approximate the tape 
position with the fast forward 
key just before where the 
program would start, and then 
LOAD the program with the name 
of the program using the 
format IOAD "NAME CF 
PROGRAM” . 

Sane of our subscribers 
have told us that they could 
not get the programs to load 
by name but they would load 
with the double quotes. Others 
have told us that the loader 
program wouldn't load certain 
programs. Most have told us 
that all the programs could be 
loaded either way. Every 
custaner's cassette is made 
fran the same master tape, so 
the programs on everyone's 
cassettes are identical . We 
feel it is most probably a 
problem of volume adjustment 
or recorder design. We have 



noticed this situation on sane 
of our recorders. 

PROGRAMS (all programs this 
month are self -running 
- program's name has inverse 
last character if 

self -running 

RT = run time/HT * load time) 

There is an approximate 7 to 
20 second pause between 
programs 

NOTE! These programs, with 
minor modification , can be 
typed into the TS-2068 . 
SCROLL, FAST & SLOW would be 
eliminated and CODES and 
numbers following CHR$ would 
have to be changed as would 
any numbers following USR, 
POKE, PEEK, PLOT or UNPLOT. 

3<£-j'Y 

"BCMB-CATCHER" LT = s 53 

The "5" and "8" arrow keys 
control the movement of a 
pillow in this game that you 
manuever to catch bombs that 
are falling. 

fS--? Y 

"LAND-MINE" LT = 1:14 

In this game, you try to 
travel through a minefield 
without hitting a land mine. 
The game starts with the 
minefield shown an the screen. 
There is a delay as the 
computer hides the mines under 
the appropriate co-ordinates. 



3 



The computer will then ask you 
how many co-ordinates you want 
to move. You will be awarded 
either positive or negative 
points each time you advance 
and your position will be 
marked. If you land on a land 
mine, you will be sent back to 
the beginning to start over. 
The game is over when you 
reach the end and your score 
will be determined by the 
amount of moves versus your 
total points. 

■3&- t l /J 

" SLOT-MACHINE " LT = 2:51 

Our thanks to Rick Blewitt 
and his father John for this 
program. It simulates the play 
of a one-armed bandit where 
the user plays with a certain 
amount of nickels. You tell 
the canputer how many and then 
sit back. 

There was no documentation 
regarding rules but it does 
give a lot of play for the 
money along with good 

"BOWLING" LT = 1:31 

Although not a full-blown 
bowling average program, it 
can be used as a base to 
include a whole league. It is 
designed to keep averages , 
high game and high series for 
one team. 

Start the program with 



prompt #1 and enter requested 
data for how many weeks in the 
season, hew many players and 
the players' names. 

Prompt #2 allows entry of 
scores cn a week by week 
basis. Prompt #3 can have the 
data displayed and pranpt #4 
will allcw players' names or 
scores to be edited. Pranpt #5 
allows the data to be saved on 
tape with a file name. 

VC,L tf/o i >r-3<5j 

"MINICALC" LT = 1:30 

Here is a mini -vers ion of 
the Vis i -Calc type programs. 
The program starts with a 3 by 
7 grid with a blinking cursor 
at the i_pper left box. The 
cursor can be moved with the 
shift/arrow keys to any box. 
The "B" key brings it to the 
first box and the "N" key to 
the last box . The other 
cartnands are as follcws: 

"V" - allows entry of a 

numeric value 

"F" - allows entry of a 

formula 

"D" - displays the formula in 
the cursor box 

"C" - calculates the formula 
in the cursor box 

A simple example for use of 
this program might be for a 
simple payroll application . 
Let us say that we have 2 
employees, one makes $4.51 per 
hour and the other $5.25 per 
hour. With the cursor in box 



4 



A1 press the "V" key. New 
enter "4.51" and press enter, 
move the cursor to box A2, 
press the "V" key again and 
enter "5.25". Now move the 
cursor to the A3 box and using 
the same value format, alter 
"40" for 40 hours worked for 
each employee. Now go to box 
A4 and press the "F" key. We 
want to multiply the hourly 
wage in box Al times the hours 
worked in box A3 so enter 
"A1*A3". 

The box will now contain a 
graphic "F" in it. If we ever 
want to check the formula in 
this box, we need only move 
the cursor to it and press the 
"D" key and the formula will 
be dispayed at the bottom of 
the screen until we press any 
key but BREAK (try it now). 

New position the cursor in 
box A5 and enter the formula 
"A2*A3" the same way. 

You may new calculate 
either of the formulae by 
putting the cursor in the 
appropriate box and pressing 
the "C" key. The box will then 
display the appropriate sum 
until any key (except BREAK) 
is pressed . Formulae can 
contain the logical operators 
<+>, <->, <*>, </> and <**> 

and be up to 32 characters 
long. They can be longer but 
an error will occur if you 
want to display them. 

Even though this program is 



limited to only 21 boxes and 
does not have duplication and 
replication or print-out 
features (add a COPY caimand 
with appropriate input for 
print -out), it is extremely 
powerful and easy to use and 
would make an excellent base 
for a more sophisticated 



—version. 

* vatr 

2-Z^->-S<Z 



"BULLETIN" 



Our bi-monthly bulletin 
board program. Pressing "P" 
pauses the scroll. Pressing 
any key restarts it. Pressing 
H B" makes it move backraxds 
and "F 11 makes it go f award. 




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5 




TIME-STAR COMPUTERS 



Details are sketchy at this 
time but there is a company 
that is planning to acquire 
merchandising rights to the 
Timex 1500 and 2068 computers. 
In a conversation with David 
Higgenbottan of Trinity Magnum 
Co. in California, a bold plan 
to sell these computers aider 
the TIME-STAR name through a 
nation-wide chain of new 
stores . Called "THE LITTLE 
COMPUTER STORE", a franchise 
system is being developed. 

After - mar ket software and 
hardware companies are also 
being contacted regarding 
their products. The customer 
could enter the store and 
purchase both hardware and 
software on the spot. Over 48 
companies so far have 
expressed interest. 

These stores might also 
sell other in-expensive micros 
with related software and 
hardware . One of the big 



attractions would be that 
software duplication would be 
done on location and that 
consumers could examine 
programs on the computer 
before purchase . 

Mr. Higgenbottan sees the 
effort as a metamorphisis for 
the Timex market with in-roads 
to be developed in educational 
institutions . 

We wish him luck and 
success and will help in any 
way we can. For further 
information , contact Mr . 
Higgenbottan at (1-213) 
864-7068 . 



CONVERSION PROBLEMS 



People have been contacting 
us regarding problems with the 
software programs designed to 
convert TS-1000 programs to 
TS-2068 programs. Without 
mentioning manufacturing 
names, the ones mentioned to 
us would oily give partial 
success. 

We experienced problems 
with the ones we used also 
except with one, and certain 
rules had to be followed to 
the letter. 

The one we had the best 
lixk with was the one 
published in SYNTAX (Dec/83 
issue - 1-617/456-3661 RD 2, 



6 




BOX 457, HARVARD, MA, 01451) 
called FIRSTLOADER which is 
also available on tape for 
$19.95 from E-Z Key, Suite 
75-stx 711 Southern Artery, 
Quincy, MA, 1-617/773-1187. 

When using this or any of 
the 1000/2068 conversion 
programs , I cannot stress 
enough the importance of 
adhering to the following 
guidelines . 

- Make sure the 1000 tape has 
been prepared as clean and 
free of noise pulses as 
possible. Disconnect the EAR 
plug when making the 1000 
copy. Ruining the recorder on 
batteries rather than A/C 
helps. Purchased software from 
vendors is usually noise free 
and copies don't have to be 
made. 

- Once the conversion program 
is in the 2068, advance the 
1000 program in the recorder 
to the segment just before the 
program starts . This segment 
usually lasts for about 5 
seconds and should be 
completely noise free. Listen 
to it with the cords 
disconnected. If there is 
noise in this portion, there 
most probably will be noise 
thoughout the program. The 
conversion program will 
identify these noise pulses as 
part of the program and either 
banb or result in a garbled 
conversion. 



The FIRSTLOADER version has 
the advantage of keeping the 
machine language conversion 
program in memory after the 
conversion is complete. If the 
user uses the DELETE command 
to erase the program and CLEAR 
to clear the variables , 
FIRSTLOADER can be called 
again with the U5R ccmand to 
convert the next program. NEW 
will however, destroy 
FIRSTLOADER. 

Converted programs will 
have any inverse characters 
converted to normal upper-case 
characters. Line numbers with 
nothing after them usually 
signify cawnands or functions 
not in the 2068 vocabulary 
such as SLOW, FAST, PLOT 
(different on the 2068), 
UNPL0T, SCROLL and Shift "Q" 
("") and must be edited 
accordingly . The numbers 
following canmands or 
functions such as CHR$, CODE, 
PEEK, POKE, PLOT and USR must 
be changed or re-formatted to 
operate properly. 

The FIRSTLOADER version we 
used was typed in from the 
SYNTAX issue and occupies 
about 1/2 K of upper memory. 
It worked every time with the 
1000 programs we converted , 
but keep in mind, we have 
equipment that can make very 
clean copies. 

Using this program may mean 
a lot of time-saving cn your 
part for those favorite 



7 



programs you were going to sit 
down and type in fran 
scratch . 

1000 HI -RES 



We saw a demonstration of 
hi -resolution graphics on the 
TS-1000 and were amazed. 
Without any hardware changes, 
either the SW-HI-RES program 
($20.00) or the HI -RES WORD 
PROCESSOR ($24.95) can be 
loaded fran cassette tape . 
Screen resolution is 174 by 
255 pixels. 



intact. The BASIC program that 
a bunch of 
machine-language sub-routines, 
can be broken at any time. The 
screen, however, will not 
revert back to normal unless 
the proper USR canmand is 
executed . When another user 
command is used, the Hi -Res 
picture instantly returns. 

The program seens to use 
two areas of memory to map the 
screen and the USR calls allow 
you to toggle back and forth. 
Whichever one is used , the 
other is completely eliminated 
from the screen. 



New commands with the 
SW-HI-RES program include 
PLOT, UNPL0T, PRINT, PRINTC, 
DRAW, CLS, 9CROL-UP, DOWN, 
LEFT, RIGHT & COPY. Print-out 
to the 2040 printer is 
possible. You can create your 
own character set and it canes 
with a sample graphics 
generator - that plots a 
hi -resolution picture of 
circles and sine waves to the 
screen. 

The only drawback we could 
see was that the graphics 
generation took a considerable 
amount of time, however, 
pictures could be saved on 
tape and recalled instantly 
when loaded. 

The High resolution 
graphics are generated to the 
top 22 lines of the screen 
with the bo t. tan two lines left 



For further information , 
contact N. ELMALEH, 5100 
HIGHBRIDGE STREET 53 , 
FAYETTEVILLE, NY, 13066 




. . 8 





SIMULATING DRAW & CIRCLE 
CM THE TS-10Q0 



Good morning , Class ! 
Today's session will be on 
screen graphics for the 
TS-1000. 

Unlike the TS-2068, the 
1000 does not have commands 
such as DRAW and CIRCLE. These 
contends can be simulated with 
routines, however, the hi -res 
graphics will be missing. 

To simulate the DRAW 
contend, enter the following 
program: 

10 LET X=0 
20 LET Y=X 
100 INPUT XX 
110 INPUT YY 
120 LET A=X-XX 
130 LET B=Y-YY 

140 LET C=( A AND ABS A>=ABS 
B) 

+ (B AND ABS B>ABS A) 

150 IF C=0 THEN LET 0.1 
160 FOR N=0 TO C STEP SO) C 
170 PLOT X+A/C*-N ,Y+B/C*-N 
1 180 NEXT N 

. 190 LETT X=X+A/C*-N 

' 200 LET Y=Y+B/C*-N 

210 GOTO 100 



This routine starts the 
first plotted point at the 
lower left hand of the screen 
and is determined by the "X" 
and "Y" values in lines 10 and 
20, These of course can be 
changed. 

The inputs fran lines 100 
and 110 ask for the pixel 
position that the line is to 
be drawn to. The first input 
would be hew many pixels fran 
the left border (1 to 62) and 
the next input is for how many 
pixels fran the bottom (1 to 
42). Enter "20 ■ and "10" for 
these inputs and a diagonal 
line will be plotted and the 
routine will recycle for the 
next inputs. 

Now enter two new screen 
co-ordinates and a new line 
will be drawn fran the last 
plotted pixel to the new 
destination . The starting 
pixel position of the new line 
is determined by lines 190 and 
200 which reset the X/Y 
values. 

Line 140 does all the hard 
mathematics and the program 
uses various trig functions 
which perform quite quickly 
canpared to other IF/THEN 
canpariscn techniques that are 
ccrmon ly used. 

Unlike the TS-2068 version 
of DRW, this routine simply 
asks for the screen positions 
that the line is going to be 
plotted to and draws the line 



9 



to that position fran the end 
of the last line. With this 
method you will not 
accidentally draw a line off 
the screen where an error 
message will occur as long as 
you stay within the specified 
parameters . 

By changing the following 
lines to read: 

190 INPUT X 
200 INPUT Y 

you can start the new lines at 
any position you want. 

But so much for straight 
lines (almost straight). What 
about curved lines , circles 
and ellipses? Biter the 
following simple program: 

10 INPUT A 
20 INPUT B 

100 FOR 1=0 TO 2*PI STEP 
PI/30 

110 PLOT 30+A*006 I,B+fi*SIN I 
120 NEXT I 

Line 10 inputs the width of 
the ellipsoid and line 20 
inputs the height. If the two 
inputs are the same, a circle 
will result. 

Now, what about curves? If 
we look at line 100 we see the 
segment "2*PI" . This 

represents the circumference 
of the circle or ellipscftd. If 
the "2*" were missing, only 
half of the circle or 
ellipsoid would be plotted. If 



you wanted only a fraction of 
the ellipsoid to appear, add 
and change the following 
lines: 

30 INPUT C 

100 FOR 1=0 TO 2*PI*C STEP 
PI/30 

The variable "C” would 
determine the fraction of 
ellipsoid to be plotted 
would be altered with line 
with an input between .1 
1 . 

Class dismissed! 




Of the Earth's 

196,949,970 square 

miles of area, 48 million 
square miles of its 

surface are always snow- 
covered. 




According to Figgie 
International^ Ther- 
mometer Corporation of 
America (TCA), it takes 
more than 1,000,000 ice 
crystals to cover two 
square feet with 10 
inches of snow. 



10 






different. 




Certain machine language 
programs, including cnes fran 
Synchro-Set te , will not run on 
my ZX-81 resulting in an error 
message - yet, when I put the 
same tape into try friend's 
TS-1000, it runs with no 
problem. 



We have checked the 
listings and they appear 
identical . We switched 
Repacks (mine is a BYTE -BACK 
16K and his is the Timex 16K) 
and the problem seems to 
follow the BYTE -BACK RAMpack. 

Is my RAMpack faulty? Other 
programs seem to run with no 
trouble . 

J. Thomas - Lincoln, NE 



Dear Jerry, 

The explanation we got was 
that on the earlier BYTE-BACK 
RAMpack s , certain RAM memory 
locations conflict USR call 
functions where-ipon the 
design of the TS RAMpack is 



Users have been telling us 
that non -Timex RAMpacks will 
not operate on the TS-1500 
either, with a variety of 
malfunctions - Ed. 



Dear Ed, 

Does the S & S Company have 
any future plans regarding any 
kind of subscription computer 
publications? 

L. Peaslee - Bronx, NY 



Dear Len, 

Not at this time. One of 
the big problems regarding 
Synchro-Sette is the lack of 
material to put into the 
magazine . Programs can be 
written cn almost every 
conceivable subject but 
newsworthy topics are becoming 
harder to cane by . Sane 
catpanies that supplied 
software, hardware and news 
information which were viable 
a few months ago are no longer 
in business now. 

On the other side of the 
coin, the purchasing customers 
of Timex equipment have 
dwindled to the point where 
many of the supporting 
canpanies feel the odds are 
against them to advertise 



11 



their wares in any 
publication . 

Perhaps the TIME-STAR 
program (see Editor Ramblings 
This issue) will turn this 
around . I think most 
supporting companies have 
developed a "wait and see" 
attitude before they rrake any 
caimitments . 

We will continue to support 
the Timex computers as long as 
there is a market - Ed. 



Dear Ed, 

I purchased a IS- 20 68 from 
Timex at the close-out price 
of $99.95 and an wry 
impressed with it . I was 
particularly impressed with 
your "SPIDERS" program in the 
January 1984 issue. I wish the 
volume of the sound output 
could be increased and there 
was a 80 column output 
device. 

But for 100 bucks, this is 
the best deal going! I'm sad 
to see your publication phase 
out. I realize the number of 
subscribers aren 't there 
anymore but I have learned a 
great deal fran your magazine 
and cassette programs and will 
stay with you to the end . 
Thanks again. 

S. Greenstein - Colorado 
Springs, 00 



Dear Sherwin, 

We are also saddened at the 
outcome, but who knows what 
the future will hold - Ed. 



m 



???????? 

????????? 

??????? 

7mm 

???????? 

??????> 



777777777777777777717777717 
Which country is setting 
records for production by 
its dairy cows, even though 
that country is one of the 



smallest in the world? 




Although most people 
expect cows to thrive on a 
diet of water, grass and 
grain, this country's cattle 
have learned to love a com- 
puter-prepared menu of to- 
mato pulp, orange peels, 
silage and residues from 
beer and cheese production. 
Statistics show they’re thriv- 
ing and so is milk produc- 
tion. Can you name the 
country? 

ANSWER: The country 
is Israel. Thanks to comput- 
erized genetic planning, its 
cows have helped that coun- 
try achieve the highest milk 
production in the world. 
Since water, grass and grain 
are three items lacking in 
that arid land, its scientists 
have come up with a diet 
that seems to work won- 
ders. The country’s dairy 
farmers say they still have 
much to 1 earn from Ameri- 
can farmers but report that 
one of their success secrets 
is the fact that ALL of their 
dairies are high producers. 



12 




A SCREEN MEMORY MAPI 
FOR THE 1S-3.068 J 



Cn the TS-1000 we learned 
that the screen could be 
addressed directly by PCKEing 
numeric values directly into 
certain memory locations. The 
locations that were to be 
PQKEd depended cn how much 
memory the program in the 
canputer took xp. The memory 
locations for the screen 
resided in an area above the 
program memory and was said to 
"float”. The first screen 
location could be determined 
with the formula "LET X = PEEK 
16396 + 256 * PEEK 16397 + 
1 ". 

We also learned that the 
screen was stored in memory as 
24 lines of 33 characters each 
for a total of 792 memory 
locations. The first 32 
characters of each line cn the 
screen would have their CODE 
numbers held in memory and 
could be changed by PCKEing 
that memory location with a 
different number. 

The last row or character 
should not be PCKEd because it 
held a value of 118 which, 



when altered, would cause the 
program to crash. 

Try as I may, I could not 
find an area in the TS-2068 's 
memory that held the CODE 
numbers of the characters on 
the screen. 

There is a good reason for 
this! None of the techniques 
used to hold screen 
information for the 1000 are 
used in the 2068, as far as 1 
can see! 

The CODE numbers of the 
screen characters are not held 
in memory but exact screen 
information is retained in 
memory in a very devious and 
complicated way. 

On page 265 of the owner's 
manual we find that the screen 
DISPLAY FILE resides in the 
memory locations between 
400Q-57FF hex or 16384 to 
22527 decimal. Unlike the 
1000, whose screen memory nap 
floats, the 2068 's screen map 
resides in a stationary area. 
This should make it easy to 
address , right? Read cn 

One day, while trying to 
POKE these locations with 
character CCDEs , I discovered 
I was winding up with seme 
weird arrangement of dots 
ranging fran cne dot to a line 
of 8 dots. 

The answer was obvious! The 
characters cn the screen were 



13 



not being held in memory by 
their individual OODE numbers 
but with a total of 8 numbers 
for each character . Each 
character was represented by 
an 8 by 8 matrix where each 
line was represented by the 
visual represen tat ion of an 8 
digit binary number. The 
letter "A" would therefore be 



seen as; 



0000 0000 
00111100 
01000010 
01000010 
01111110 
01000010 
01000010 
00000000 



(0) 

(60) 

( 66 ) 

(66) 

(126) 

(66) 

(66) 

( 0 ) 



The 0s and Is on the left 
side are the binary numbers of 
the letter "A" where the 0's 
are visually displayed on the 
screen as "null" or blank dots 
(PAPER colour) and the Is are 
displayed as solid dots (INK 
colour). The numbers to the 
right of the binary numbers 
are their decimal equivalent 
and it is these that are 
stored in memory . In other 
words , it takes 8 numbers, 
stored in memory, to hold the 
information for each screen 
character . The amount of 
screen locations are 32 
characters per line (not 33 as 
on the 1000) for 24 lines for 
a total of 768 positions. 8 
decimal BIN numbers are in 
memory for each screen 
character for a total of 6144 
RAM memory locations (6K) to 



hold the entire screen map. 

Now comes the complicated 
part! The screen is divided 
into 3 sections of eight lines 
each. The top third section 
resides in RAM at locations 
16384 to 18431, the middle 
third at locations 18432 to 
20479 and the bottom third at 
locations 20480 to 22527. The 
locations for the lines of 
bit-graphics for each 
character are not consecutive 
as can be demonstrated by the 
following program: 

100 FOR N=16384 TO 22527 
110 PCKE N,1 
120 PRINT AT 21,20;N 
130 NEXT N 

This routine PCKEs a single 
dot to the screen at every 
possible bit-graphics (BIN) 
location . You will notice that 
the screen is scanned in 3 
sections with each section 
being scanned 8 times . The 
following routine produces a 
screen grid (bottom 2 lines 
not in grid) for easy 
visualization and asks the 
user for 2 inputs. The first 
is the character you want to 
be POKED from the screen and 
the second is a co-ordinate. 
Enter either an alphabetic, 
numeric or graphic character 
for the first pranpt. For the 
second pranpt the following 
parameters must be observed: 

TOP THIRD OF SCREEN - 0 TO 

255 



14 



(continued on back page) 




The TS-2068 has sane unique 
graphics capabilities as most 
users already know. PLOT 
allows Hi -Res plotting of any 
screen pixel. DRAW allows 
straight lines (as nearly as 
the computer can make them) 
between the last plotted pixel 
to the new co-ordinates. 
CIRCLE makes a circle with a 
slight eliptical shape. 

There is no catmand to draw 
elipsoids directly or for that 
matter, a more perfect circle. 
The DRAW canmand, however, can 
also draw circles or parts of 
circles. A pixel has to be 
plotted on the screen first 
that would be far enough a way 
fran the borders so that the 
DRAW routine does not run out 
of roan. 

DRAW followed by 2 numbers, 
separated by a comma, normally 
plots a straight line to the 
co-ordinates of the 2 numbers. 
If a caima and third number 
follow, a curved line will 
result. The straight line 
distance between the two 
points is still the same as if 



cnly 2 numbers were used but 
the curve will occur between 
the points . Biter the 
following program; 

100 INPUT A,B 
110 CLS 
120 PLOT 50,50 
130 DRAW A,B 
140 PAUSE 40000 
150 CLS 

160 PLOT 50,50 
170 DRAW A,B,PI 
180 PAXE 40000 
190 CLS 
200 PLOT 50,50 
210 DRAW A, B, PI/2 
220 GOTO 100 

Experiment with inputs such 
as 50,50 and 30,60 etc. You 
will notice the slope of the 
curve changes each Hire in 
proportion to the value of the 
third number. Edit lire. 170 to 
read: 

170 DRAW A,B,PI * x 

where "x" equals a number 
in between .1 and 1.65. You 
new have an indication of how 
this third number affects the 
curve. 

The CIRCLE ccmnand cannot 
draw a perfect circle but a 
routine can be written that 
can draw a circle as perfect 
as the computer is capable. It 
can also draw elipsoids. 

The following program will 
draw a pretty good ellipse 
with only 9 program lines. 



15 



10 INPOT "Length? " ; 1 : LET 

C=1 

20 INPOT "Height? ";h: IF H<C 

THEN LET c=h 

30 CLS : LET b=l/(l4h): LET a 
= h/tl+h) 

40 PLOT c,c 
50 DRW l,0,PI*a 
60 DRW 0,h,PI*b 
70 DRAW -l,0,PI*a 
80 DRAW Q,-h,PI*b 
90 GOTO 10 

The length input will be an 
approximation of the length 
fran left to right and the 
height fran qp to dawn. 

The program actually plots 
the elipsoids as 4 parts, each 
the part of a circle 
determined as a fraction of 
its circimfrence by lines 50 
to 80. 

The variable "c" in lines 
10 and 20 determines the 
starting PLOT positions in 
line 40 so that the greatest 
amount of elipsoids can be 
tested. 

The Variables "a" and "b" 
determined by line 30 and used 
in lines 50 determine the 
portion of the circle to be 
used in each of the 4 elipsoid 
segments which line ip 
perfectly to give as true an 
elipse as can be expected. 
Ranove the CLS carmand in line 
30 to get an overlay cn your 
screen . 

If the length is 25% 



greater than the height , a 
near perfect circle will be 
drawn such as if length = 50 
and height = 40. 

Print-out to the 2040 
printer, however, still shows 
sane elongation upwards so 
experimentation is needed to 
get the correct results. This 
is a useful routine wherever 
screen graphics requiring 
circles or elipsoids are 
needed such as drawings , games 
or business charts - Ed. 



(SCREEN CONTINUED ) 

MIDDLE THIRD - 2048 TO 

2303 

BOTTCM THIRD - 4096 TO 

4351 

The character you alter for 
the first prompt will appear 
in the upper left hand comer 
of the screen . The second 
pranpt must have a number 
entered that fits into the 
range above. The character 
will then be POKED to the new 
screen location, byte by 
byte. 

This routine nay help you 
write a program in which you 
can create your .awn hi -res 
screen graphics to cover the 
entire screen. All you have to 
do is determine the. BINARY 
image of each graphic 
character you want to appear, 
convert the binary numbers 
into decimal and POKE than 
into the proper memory 
locations - Ed.